1. Field of the Invention
The present invention is related to a toughening agent for an epoxy resin composition; and more specifically, the present invention is related to a high molecular weight poly(propylene oxide) polyol toughening agent for use in epoxy resin compositions.
2. Description of Background and Related Art
There are various known methods for toughening epoxy thermosets using a number of available known toughening agents such as for example using core-shell rubbers as toughening agents. In another example, U.S. Pat. No. 4,497,945 discloses the use of a low molecular weight (1000-3000 daltons) poly(propylene oxide) diol or triol as a toughening agent for epoxy-anhydride thermosets. The low molecular weight polyol known in the above prior art has the disadvantage of decreasing the glass transition temperature (Tg) of the resulting thermoset system.
It is therefore desired to provide a curable epoxy resin system with a toughening agent that will (1) improve the toughness of the epoxy resin system without decreasing or detrimentally affecting the Tg of the final thermoset made from the epoxy resin system; and (2) not detrimentally affect the properties of the final thermoset system.